Support for sub- & superscript, without using html tags

[PeterHagen]

Describe the feature
Currently marked.js doesn't seem to have support for sub- & superscript, without using html tags. This would be possible by using E=MC^2^ and log 2~a~ as examples

Why is this feature necessary?
It would compliment the overal usability of marked.js, which would make reading and writing the markdown much cleaner instead of using html in the text.

Describe alternatives you've considered
As described on subscript-in-markdown, and I'm not sure if this is documented anywhere else, using E=MC^2^ would result in superscript, while log 2~a~ would result in subscript. Unfortunately, GitHub also doesn't support it.

[UziTech]

Also ~this is strike through~

this is strike through

So which one would override the other for GitHub?

[PeterHagen]

The subscript method should not allow spaces in the text and I guess it’s only valid when written against a character or word. Something like CO~2~. In some markdown parsers, strike through requires 2 ~ I noticed.

[UziTech]

You could create an extension for these something like:

// superscript.js
export default {
  name: 'superscript',
  level: 'inline',
  start(src) { return src.indexOf('^'); },
  tokenizer(src) {
    const match = src.match(/^\^(\w+)\^/);

    if (!match) {
      return;
    }

    return {
      type: 'superscript',
      raw: match[0],
      text: match[1]
    };
  },
  renderer(token) {
    return `<sup>${token.text}</sup>`;
  }
};

// subscript.js
export default {
  name: 'subscript',
  level: 'inline',
  start(src) { return src.indexOf('~'); },
  tokenizer(src) {
    const match = src.match(/^~(\w+)~/);

    if (!match) {
      return;
    }

    return {
      type: 'subscript',
      raw: match[0],
      text: match[1]
    };
  },
  renderer(token) {
    return `<sub>${token.text}</sub>`;
  }
};

import superscript from './superscript.js';
import subscript from './subscript.js';
import { marked } from 'marked';

marked.use({
  extensions: [
    superscript,
    subscript
  ]
};

console.log(marked.parse('test^superscript^ test~subscript~'));
// <p>test<sup>superscript</sup> test<sub>subscript</sub></p>